Original ArticleBifurcation Location Is Significantly Associated with Rupture of Small Intracranial Aneurysms (<5 mm)
Introduction
The prevalence of unruptured intracranial aneurysms (UIAs) is 1%–7%.1 The most serious damage caused by UIAs is a result of subarachnoid hemorrhage (SAH), which has a 30-day mortality of 40%.2 The rupture risk is known to increase with increasing aneurysm size.1, 3, 4 Thus, most small UIAs (<5 mm) are believed to be associated with a low risk of rupture. However, several studies5, 6 have reported the rupture of small aneurysms. Kassell et al.7 assessed 1092 cases to analyze the size distribution of ruptured aneurysms and found that 13% of ruptured aneurysms were <5 mm in diameter. A study by Kashiwazaki et al.8 clearly showed that approximately 30% of ruptured intracranial aneurysms (RIAs) were small (<5 mm) and that some small UIAs also had a risk of rupture.9, 10, 11, 12
Several previous studies have investigated the risk factors of rupture in patients with small UIAs. In the Japanese Small Unruptured Intracranial Aneurysm Verification study,9 the rupture of small UIAs was found to be related to age, hypertension, and the presence of multiple aneurysms. However, those prospectively studied groups did not include small aneurysms that had been previously treated, and many patients with small UIAs that may have been at high risk of rupture were treated and were not enrolled into the studies. Kashiwazaki et al.8 found that size ratio (SR) might predict the risk of rupture in small UIAs, but the potential risk factors of rupture included in that multivariate analysis may be insufficient, and no systematic analyses of the risk factors for rupture of small UIAs are available.
We tried to analyze as many factors associated with the rupture of small IAs as possible to investigate the predictors of rupture in a large cohort of patients with small UIAs and RIAs.
Section snippets
Study Design and Ethics
This was a retrospective study. The design was approved by the review committee of Beijing Tiantan Hospital, and informed consent was obtained from all participants.
Patient Selection
We retrospectively reviewed consecutive patients who attended our institution with small intracranial aneurysms (IAs) (<5 mm) from February 2009 to December 2014. All patients in this study were examined using three-dimensional rotational angiography. All patients with SAH were examined using computed tomography. All patients
Study Population
A total of 548 consecutive patients with 618 small aneurysms, including 267 RIAs and 351 UIAs, were included in this study. Seventy-six patients were excluded for the following reasons: the location of the ruptured aneurysm could not be identified (n = 20); inability to find the digital subtraction angiography image (n = 12); fusiform, traumatic, or dissecting aneurysm (n = 16); or aneurysms that were related to cerebral arteriovenous malformation, arteriovenous fistula, or moyamoya disease (n
Discussion
In this study, the main finding was that location at parent artery bifurcations in the circle of Willis or in the posterior circulation, higher SR, younger age (<50 years), and hypertension were risk factors of rupture in small UIAs.
Conclusions
This study showed that 70.4% of small RIAs (<5 mm) were located at parent artery bifurcations and bifurcation location was a significant independent factor for the risk of rupture of small UIAs (<5 mm). Prophylactic treatment should be recommended for small UIAs (<5 mm) in this location. Higher SR, location in the posterior circulation, younger age (<50 years), and hypertension were also independent factors associated with the risk of small UIA rupture, and more prospective studies are needed
Acknowledgments
A.L. conceived and designed the experiments. X.F. and W.J. performed the experiments. X.F. and H.K. analyzed the data. Z.Q., P.L., X.W., W.X., Y.L., and C.J. contributed reagents, materials, and analysis tools. X.F. and W.J. wrote the article. Z.W. revised the manuscript.
References (33)
- et al.
Unruptured intracranial aneurysms: epidemiology, natural history, management options, and familial screening
Lancet Neurol
(2014) - et al.
Hydrogel-coated coils versus bare platinum coils for the endovascular treatment of intracranial aneurysms (HELPS): a randomised controlled trial
Lancet
(2011) - et al.
Molecular basis of the effects of shear stress on vascular endothelial cells
J Biomech
(2005) - et al.
Cause-specific mortality of 1-year survivors of subarachnoid hemorrhage
Neurology
(2013) - et al.
Guidelines for the management of patients with unruptured intracranial aneurysms: a guideline for healthcare professionals from the American Heart Association/American Stroke Association
Stroke
(2015) - et al.
Size of intracranial aneurysms
Neurosurgery
(1983) - et al.
Size and location of ruptured intracranial aneurysms
J Korean Neurosurg Soc
(2009) - et al.
Rupture of very small intracranial aneurysms: incidence and clinical characteristics
J Cerebrovasc Endovasc Neurosurg
(2015) - et al.
Complex hemodynamic insult in combination with wall degeneration at the apex of an arterial bifurcation contributes to generation of nascent aneurysms in a canine model
AJNR Am J Neuroradiol
(2014) - et al.
Size ratio can highly predict rupture risk in intracranial small (<5 mm) aneurysms
Stroke
(2013)
Small unruptured intracranial aneurysm verification study: SUAVe study, Japan
Stroke
Unruptured intracranial aneurysms-risk of rupture and risks of surgical intervention
N Engl J Med
Natural history of small unruptured anterior circulation aneurysms: a prospective cohort study
Stroke
Hypertension, age, and location predict rupture of small intracranial aneurysms
Neurosurgery
Difference in aneurysm characteristics between ruptured and unruptured aneurysms in patients with multiple intracranial aneurysms
Stroke
Assessment of intracranial aneurysm rupture based on morphology parameters and anatomical locations
J Neurointerv Surg
Cited by (12)
The Association of Morphological Differences of Middle Cerebral Artery Bifurcation and Aneurysm Formation: A Systematic Review and Meta-Analysis
2022, World NeurosurgeryCitation Excerpt :Currently, the treatment of UIAs is controversial, especially for small UIAs (<5 mm). Feng et al.44 have shown that bifurcation location was a significant independent factor for the risk of rupture of small UIAs by a follow-up of 548 patients with 618 small UIAs. Some studies have suggested that a larger bifurcation angle causes aneurysms to rupture at a smaller size compared with a smaller bifurcation angle.43
Relationships between aneurysmal wall enhancement and conventional risk factors in patients with intracranial aneurysm: A high-resolution MRI study
2019, Journal of NeuroradiologyCitation Excerpt :A recent study showed that IAs located at bifurcations are a risk factor for rupture of small IAs [12]. According to previous studies, bifurcation areas of arteries are known to be vulnerable sites where the arterial wall is weak and associated with hemodynamic stress changes [12,22]. In this study, IAs located at bifurcations were more likely to showed AWE, whereas it exhibited no relationship upon multiple analysis.
Bifurcation Location and Growth of Aneurysm Size Are Significantly Associated with an Irregular Shape of Unruptured Intracranial Aneurysms
2017, World NeurosurgeryCitation Excerpt :Maximum height was defined as the largest length from the neck to the tip of the aneurysmal dome tip.19 Maximum width was defined as the largest length of the dome perpendicular to its height.20 Aneurysm size was defined as the largest of these measurements.21
Conflict of interest statement: This research was supported by the Natural Science Foundation of Beijing, China (no.7142032) and Specific Research Projects for Capital Health Development (2014-3-2044).
Xin Feng and Wenjun Ji contributed equally to this work.